1. Field of the Invention
The present invention generally relates to an oil pump apparatus. More particularly, the present invention relates to an oil pump apparatus including an inner and outer rotor which are disposed in a housing and including a shaft connected to the inner rotor to rotate the outer rotor.
2. Background of the Invention
The type of an oil pump apparatus is described in Japanese unexamined Patent Publication No. Shou. 63-223382. This apparatus includes an inner rotor, an outer rotor, a housing and a crank shaft. The inner rotor is formed in a ring shape, and rotational force is transmitted from the crank shaft. Further, the inner rotor has a ring shaped projection at the inner peripheral surface. The projection of the inner rotor extends along the outer peripheral surface of the crank shaft. The housing includes a receiving position which receives the projection of the inner rotor so as to set a position of the inner rotor. Therefore, the precise manufacturing of the inner rotor and the housing are required.
Because the projection of the inner rotor slides toward the housing and is pressed against the housing, there is rotational resistance between the projection of the inner rotor and the receiving position of the housing. This results in problems due to the wearing out of the receiving position of the housing.